This baseline risk assessment of ground water contamination of the uranium mill tailings site near Falls City, Texas, evaluates potential impact to public health and the environment resulting from ground water contamination at the former Susquehanna Western, Inc. (SWI), uranium mill processing site. This document fulfills the following objectives: determine if the site presents immediate or potential future health risks, determine the need for interim institutional controls, serve as a key input to project planning and prioritization, and recommend future data collection efforts to more fully characterize risk. The Uranium Mill Tailings Remedial Action (UMTRA) Project has begun its evaluation of ground water contamination at the Falls City site. This risk assessment is one of the first documents specific to this site for the Ground Water Project. The first step is to evaluate ground water data collected from monitor wells at or near the site. Evaluation of these data show the main contaminants in the Dilworth ground water are cadmium, cobalt, fluoride, iron, nickel, sulfate, and uranium. The data also show high levels of arsenic and manganese occur naturally in some areas.

Surface remedial action will be completed at the Falls City, Texas, Uranium Mill Tailings Remedial Action Project site in the spring of 1994. Results of water sampling activity from 1989 to 1993 indicate that ground water contamination occurs primarily in the Deweesville/Conquista aquifer (the uppermost aquifer) and that the contamination migrates along four distinct contaminant plumes. Contaminated ground water from some wells in these regions has significantly elevated levels of aluminum, arsenic, cadmium, manganese, molybdenum, selenium, sulfate, and uranium. Contamination in the Dilworth aquifer was identified in monitor well 977 and in monitor well 833 at the southern edge of former tailings pile 4. There is no evidence that surface water quality in Tordilla and Scared Dog Creeks is impacted by tailings seepage. The following water sampling activities are planned for calendar year 1994: (1) Ground water sampling from 15 monitor wells to monitor the migration of the four major contaminant plumes within the Deweesville/Conquista aquifer. (2) Ground water sampling from five monitor wells to monitor contaminated and background ground water quality conditions in the Dilworth aquifer. Because of disposal cell construction activities, all plume monitor wells screened in the Dilworth aquifer were abandoned. No surface water locations are proposed …

The uranium processing site near Falls City, Texas, was one of 24 inactive uranium mill sites designated to be remediated by the U.S. Department of Energy (DOE) under Title I of the Uranium Mill Tailings Radiation Control Act of 1978 (UMTRCA). The UMTRCA requires that the U.S. Nuclear Regulatory Commission (NRC) concur with the DOE`s remedial action plan (RAP) and certify that the remedial action conducted at the site complies with the standards promulgated by the U.S. Environmental Protection Agency (EPA). The RAP, which includes this summary remedial action selection report (RAS), serves a two-fold purpose. First, it describes the activities proposed by the DOE to accomplish long-term stabilization and control of the residual radioactive materials at the inactive uranium processing site near Falls City, Texas. Second, this document and the remainder of the RAP, upon concurrence and execution by the DOE, the State of Texas, and the NRC, becomes Appendix B of the Cooperative Agreement between the DOE and the State of Texas.

Historical evidence is presented for natural uranium series radioactive disequilibrium in uranium bearing soils in the Bargmann property area of karnes County on the Gulf Coastal Plain of south Texas. The early history of uranium exploration in the area is recounted and records of disequilibrium before milling and mining operations began are given. The property contains an open pit uranium mine associated with a larger ore body. In 1995, the US Department of Energy (DOE) directed Oak Ridge National Laboratory (ORNL) to evaluate the Bargmann tract for the presence of uranium mill tailings (ORNL 1996). There was a possibility that mill tailings had washed onto or blown onto the property from the former tailings piles in quantities that would warrant remediation under the Uranium Mill Tailings Remediation Action Project. Activity ratios illustrating disequilibrium between {sup 226}Ra and {sup 238}U in background soils during 1986 are listed and discussed. Derivations of uranium mass-to-activity conversion factors are covered in detail.